Australia

Although only a dozen plant families are unique to , there are 530 unique genera and many unique species within these genera. As the n fragment of prehistoric Gondwanaland drifted north, its ancient flora became the basis for the present plant systems. Increasing aridity modified this vegetation, giving much of it hardened, pointed leaves of reduced size--a condition called scleromorphy.
's native vegetation is divisible into seven types. The first type of vegetation consists of remnants of Gondwanan rain forests, with primitive flowering plants, palms, and laurels. These occur where high rainfall and high temperatures coincide with fertile, often volcanic soils, mainly in coastal north ...

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form a mosaic in one locality and intermingle with other plant associations. Eucalyptus trees are classified according to their bark types--hence the names stringybark, ironbark, bloodwood, and smoothbark (the gums that shed their outer bark annually). The most widespread is the river red gum. Mallee eucalypts survive in semiarid regions by growing multiple stems (lignotubers) from a common rootstock. The world's tallest flowering plant is a southern eucalyptus, the mountain ash. Its height can exceed 325 feet (100 meters). Building timbers are obtained in Victoria from alpine ash and mountain ash, in New South Wales and Queensland from blackbutt, spotted gum, bluegum, and ironbark, and in Western from jarrah and karri, another type of eucalypt.
A third type of plant community is dominated by wattles (the genus Acacia of the Mimosa family) and advances beyond the last eucalyptus trees into the desert. Although more than 900 species are known, vast regions are dominated by just a ...

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are of local importance. Finally, grasslands occur where rainfall is insufficient for larger plants. Summer-growing species tend to be more northerly and winter-growing species more southerly. Hummock grasslands (including spinifex) spread across the dunes, sandy plains, and rocky ranges of the Western Plateau.
Minor coastal plant communities include salt marsh, seagrass, and mangroves. Alpine herb fields, often flattened by the wind, are dotted with sphagnum moss bogs. Weeds introduced from outside , such as wild turnip and hoary cress, compete with crops. Lantana, blackberries, bracken fern, and Paterson's curse overrun pastures. Cape tulip and Saint-John's-wort can poison ...

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